Amount of plutonium held by Japan falls slightly with reactor restarts

Japan’s stockpile of plutonium kept inside and outside the country fell slightly at the end of 2016 from a year earlier with the restart of nuclear reactors using plutonium-uranium mixed oxide fuel, the Cabinet Office said Tuesday.

The decrease of around 1 ton to about 46.9 tons was the first decline since the end of 2012. But there remains little prospect of fully reusing the supply in the nation’s commercial reactors. The large amount of plutonium, which could be used to make nuclear weapons, remains a proliferation risk.

The Cabinet Office reported the decline to the Japan Atomic Energy Commission.

The drop was attributed to the restart of two reactors at Kansai Electric Power Co.’s Takahama plant in Fukui Prefecture that use mixed oxide fuel — known as MOX — created from plutonium and uranium reprocessed from spent fuel.

Although the government plans to draw down its plutonium supply through the use of MOX, the future of an envisioned fuel recycling project has grown increasingly uncertain.

Most nuclear plants in the country remain offline amid safety concerns following the 2011 Fukushima nuclear disaster, and MOX power generation has been planned for only a limited number of reactors.

“There may be some ups and downs in the amount possessed in the coming years, but in the long term, we believe it is important to reduce the amount and sufficiently explain the situation,” said Yoshiaki Oka, chairman of the Japan Atomic Energy Commission.

Of Japan’s roughly 46.9 tons of plutonium, about 9.8 tons was stored in Japan and the remaining 37.1 in Britain and France, where spent nuclear fuel from Japanese plants is being reprocessed.